Up-and-down motion mechanism for belt sander

ABSTRACT

An up-and-down motion mechanism for a belt sander including a continuous loop of sandpaper mounted on two end drums, includes a worktable including an opening with the belt sander moveably disposed therethrough, two bifurcations on an underside, and a housing mounted to the underside; a base releasably secured to the worktable; an electric motor in the housing and configured to repetitively move up-and-down relative to the worktable, the motor including an upper motor shaft rotatably connected to one drum, a lower worm screw, and two legs; and a transmitting assembly disposed in the housing and including a rotational shaft rotatably disposed through the legs, a worm wheel with the rotational shaft disposed through and meshing with the worm screw, two cams secured to two ends of the rotational shaft respectively, and two links each having one end connected to one arm and the other end connected to one bifurcation.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The invention relates to belt sanders and more particularly to anup-and-down motion mechanism for a belt sander, the up-and-down motionmechanism including an electric motor, two cams and a worm drive, sothat a belt sander disposed above the motor may repetitively move up ordown as the motor activates.

2. Description of Related Art

A conventional motion mechanism for a belt sander including a continuousloop of sandpaper mounted on two end drums and comprises an electricmotor, a pivotal member, a link, and a reduction gear assembly. Afteractivating the electric motor, the drums may move laterally due tooperative cooperation of the motor shaft, the pivotal member, the linkand the reduction gear assembly. As a result, the continuous loop ofsandpaper may move laterally.

However, the conventional motion mechanism for a belt sander isdisadvantageous because the movement of the belt sander is not smooth,its operation is not reliable, and the mechanism is complicated.

Thus, the need for improvement still exists.

SUMMARY OF THE INVENTION

It is therefore one object of the invention to provide an up-and-downmotion mechanism for a belt sander including a continuous loop ofsandpaper mounted on two end drums, comprising a detachable worktableincluding an opening with the belt sander up-and-down moveably disposedtherethrough, two bifurcations on an underside, a housing mounted to theunderside, a chute disposed under both one drum and the opening, and twocylindrical columns extending downward from the underside of theworktable;a base including a plurality of posts releasably secured tothe underside of the worktable; a control device mounted to the base; anelectric motor disposed in the housing and including an upper motorshaft rotatably connected to one drum, a lower worm screw, two legs, atleast one first hollow cylindrical member slidably put on onecylindrical column, and at least one second hollow cylindrical memberslidably put on the other cylindrical column; and a transmittingassembly disposed in the housing and including a rotational shaftrotatably disposed through the legs, a worm wheel with the rotationalshaft disposed through and meshing with the worm screw, two cams securedto two ends of the rotational shaft respectively, two links with theelectric motor disposed therebetween, each link having one end connectedto one arm and the other end connected to one bifurcation, and a biasingmember having one end anchored at a bottom of the electric motor and theother anchored at the underside of the worktable.

The above and other objects, features and advantages of the inventionwill become apparent from the following detailed description taken withthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a belt sander incorporating anup-and-down motion mechanism according to the invention;

FIG. 2 is an exploded perspective view of FIG. 1;

FIG. 3 is an exploded perspective view of the components shown in topright corner of FIG. 2;

FIG. 4 is a perspective view of the motor mounted on the underside ofthe worktable, and the transmitting assembly mounted to the motor;

FIG. 5 is an exploded view of FIG. 4;

FIG. 6 is a perspective view of the motor and the transmitting assembly;

FIG. 7 is a view similar to FIG. 6 showing the meshing of the worm screwand the worm wheel and their rotations in operation;

FIG. 8 is an exploded perspective view of FIG. 7;

FIG. 9 is a side elevation schematically showing a downward motion ofboth the motor and the belt sander; and

FIG. 10 is a view similar to FIG. 9 showing an upward motion of both themotor and the belt sander.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1 to 10, an up-and-down motion mechanism for a beltsander 1 in accordance with the invention is shown. The belt sander 1includes a continuous loop of sandpaper 11 mounted on two end drums 12.The up-and-down motion mechanism includes the following components asdiscussed in detail below.

A detachable worktable 2 includes an opening 21 with the belt sander 1up-and-down moveably disposed therethrough, two bifurcations 22 on theunderside, a housing 23 mounted to the underside with a portion of theopening 21 disposed thereabove, a chute 24 disposed under both one drum12 and the opening 21, and two cylindrical columns 25 extending downwardfrom the underside of the worktable 2.

A base 3 includes four posts 31 releasably secured to the underside ofthe worktable 2. A control device 4 mounted to the base 3.

An electric motor 5 is disposed in the housing 23 and includes an uppermotor shaft 51 rotatably connected to one drum 12 via an adapter 54, alower worm screw 52, two legs 53, and three hollow cylindrical members55 in which one hollow cylindrical member 55 is slidably put on onecolumn 25 and the other two hollow cylindrical members 55, alignedvertically, are slidably put on the other column 25. Both the motorshaft 51 and the worm screw 52 rotate at the speed as the motor 5activates.

A transmitting assembly 6 is disposed in the housing 23 and includes arotational shaft 61 rotatably disposed through the legs 53, a worm wheel62 with the rotational shaft 61 disposed through and meshing with theworm screw 52 to transfer motion in 90-degree, two cams 63 secured totwo ends of the rotational shaft 61 respectively, two links 64 with themotor 5 disposed therebetween, each link 64 having one end connected toone arm 63 and the other end connected to one bifurcation 22, and atorsion spring 65 having one end anchored at a bottom of the motor 5 andthe other anchored at the underside of the worktable 2.

In response to activating the motor 5, the motor shaft 51 rotates and inturn, one drum 12 rotates. Thus, the continuous loop of sandpaper 11shapes and finishes, for example wood. Generated sawdust is dischargedto a collector (not shown) through the chute 24. The subject of theinvention is discussed below.

The worm screw 52 rotates to rotate the worm wheel 62 which in turnrotates the cams 63. Further, the rotary motion of the worm wheel 62 istransformed into linear motion (i.e., repetitive up-and-down motion) ofthe links 64 due to the provision of the cams 63. Furthermore, the motor5 is capable of repetitively moving up-and-down because the cylindricalmembers 55 are slidably put on the columns 25. As a result, the beltsander 1 repetitively moves up-and-down. This has the advantages ofbalancing the load of the continuous loop of sandpaper 11 and prolongingthe useful life of the continuous loop of sandpaper 11. It is noted thatthe provision of the torsion spring 65 can assist in the returning ofthe motor 5 to its original position after being lowered or lifted.

While the invention has been described in terms of preferredembodiments, those skilled in the art will recognize that the inventioncan be practiced with modifications within the spirit and scope of theappended claims.

What is claimed is:
 1. An up-and-down motion mechanism for a belt sanderincluding a continuous loop of sandpaper mounted on two end drums,comprising: a detachable worktable including an opening with the beltsander up-and-down moveably disposed therethrough, two bifurcations onan underside, a housing mounted to the underside, a chute disposed underboth one drum and the opening, and two cylindrical columns extendingdownward from the underside of the worktable; a base including aplurality of posts releasably secured to the underside of the worktable;a control device mounted to the base; an electric motor disposed in thehousing and including an upper motor shaft rotatably connected to onedrum, a lower worm screw, two legs, at least one first hollowcylindrical member slidably put on one cylindrical column, and at leastone second hollow cylindrical member slidably put on the othercylindrical column; and a transmitting assembly disposed in the housingand including a rotational shaft rotatably disposed through the legs, aworm wheel with the rotational shaft disposed through and meshing withthe worm screw, two cams secured to two ends of the rotational shaftrespectively, two links with the electric motor disposed therebetween,each link having one end connected to one arm and the other endconnected to one bifurcation, and a biasing member having one endanchored at a bottom of the electric motor and the other anchored at theunderside of the worktable.
 2. The up-and-down motion mechanism of claim1, wherein in response to activating the electric motor, the worm screwrotates to rotate the worm wheel which in turn rotates the cams, therotary motion of the worm wheel is transformed into linear motion of thelinks, and the electric motor repetitively moves up-and-down, therebyrepetitively moving the belt sander up-and-down.
 3. The up-and-downmotion mechanism of claim 1, wherein the number of the post is four.